Cell Sheet Engineering: Thermoresponsive Harvest (2D)

Culture Dish

Culture time 36 h

Dish temperature 37.0 °C

Harvest Method

Culturing at 37.0 °C — grow the sheet, then cool below the LCST and harvest.

Live Readouts

Confluence

Adhesion strength

Intact junctions

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Cell viability

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How it works

This 2D top-down view grows cells on a dish coated with poly(N-isopropylacrylamide), PNIPAAm — a polymer with a lower critical solution temperature (LCST) of about 32 °C:

Adhesion:   A(T) = 1 / (1 + exp(-(T - Tc) / w))
            Tc ≈ 32 °C,  w ≈ 1.2 °C

Confluence: C(t) = K / (1 + ((K-C0)/C0)·e^(-r t))
            logistic growth, r ≈ 0.11 /h, K = 100%

Above 32 °C the PNIPAAm chains are collapsed and hydrophobic (high A) — cells attach, spread and form a confluent sheet, drawn here as circles wired together by thin lines representing intact cell–cell junctions. Cool the dish below Tc and the chains hydrate and swell, adhesion strength A(T) falls along the sigmoid, and the whole sheet releases from the surface as one contiguous unit — every junction line in the layer stays drawn, because thermal release breaks the polymer–cell bond, not the cell–cell bonds.

Thermal harvest — only works once adhesion has fallen (T well below 32 °C); the sheet lifts as a single connected mesh, junction integrity stays high (~90%+).
Enzymatic harvest (trypsin) — works at any temperature but proteolytically cleaves the cadherin junctions between cells; each junction line is cut individually and the cells drift apart and scatter, junction integrity collapses (~20–30%) and the tissue architecture is lost.

Watching the junction lines is the tell: in thermal release the mesh stays whole and simply moves; in enzymatic release the mesh visibly disintegrates edge by edge before the cells scatter.

Healthy cell / intact sheet Cell–cell junction Detached / damaged cell